Pump



J. C. CARTER Oct. 16, 1956 PUMP 3 Sheets-Sheet l Filed July 18, 1950 22dfnl/5172272" j/7265 Mofa/0 34d 40 39 34e in Oct. 16, 1956 J. c. CARTER2,766,698

PUMP

Filed July 18, 1950 3 Sheets-Sheet 2 15a fnl/EN fr Oct. 16, 1956 J. c.CARTER 2,766,698

PUMP` Filed July 18, 195.0 3 Sheets-Sheet 3 Jamas' '6T fate/Q UnitedStates Patent PUMP James C. Carter, Pasadena, Calif., assigner to The J.C.

Carter Company, Pasadena, Calif., a corporation of California Thisinvention relates to diffuser type centrifugal pumps adapted to delivervolatile liquids at high pressures without becoming gas bound.

Particularly, this invention relates to a diffuser type centrifugal pumpwith a shrouded impeller spanning the eye f the pump and dischargingradially into an axially extending diffuser chamber which, in turn,discharges into a concentric inner annular trough having a peripheraloutlet and wherein a deflector ring in the eye of the pump deflectsfluid leaking into the inlet from the periphery of the impeller tocreate a jet pump action which reduces the pressure head requirements atthe inlet of the pump and protects the pump from becoming gas bound.This deffection occurs along a diverging path to reduce velocity of theleaking fluid so that it is introduced into the slower moving inlet uidat a reduced velocity.

The pumps of this invention will be hereinafter specifically describedin connection with several embodiments of small, compact fuel pumps forhigh pressure delivery of volatile fuels in aircraft and guided missilefuel systems. It should be understood, however, that the principles ofthis invention are generally applicable to centrifugal pumps and it isnot intended that the illustrated embodiments should limit the inventionto any particular use, size, or weight of the pumps.

The preferred forms of pumps according to this invention include matinginlet and bearing pieces. In one form, the inlet piece has a surroundingannular trough, While in another form this annular trough is provided onthe bearing piece. In the first form, the bearing piece includes acasing surrounding the trough of the inlet piece and equipped withdiffuser vanes for directing fluid discharged from the impeller carriedbythe bearing piece into the trough. In the second form, these diffuservanes are provided on the inlet piece.

A feature of this invention includes the provision of a deflector ringin the intake piece of the pump coacting with a wear ring on the shroudof the impeller and a surrounding seal ring to deflect fluid leakingpast the rings in the direction of the intake ow into the pump.Herefofore, the leakage of fluid under pressure from a shrouded impellerwas dissipated in the inlet and the kinetic energy of the fluid waslost. The-deflector of this invention, in turning the path of theleakage flow into the direction of the intake ow, creates a jet pumpaction around the entire periphery of the incoming fiuid to not onlyreduce the required intake head pressure for efficient operation of thepump but also to prevent the pump from becoming gas bound.

Another important feature of the invention resides in the provision ofconcentric or nested axial flow paths for converting the velocity headof liquid discharged by the impeller into a pressure head withoutmaterially increasing the over-all dimensions of the pump.

Still another feature of the invention is the provision of the matinginlet and bearing pieces so that all surfaces can be easily reached forcleaning and finishing and so that the volume of the diffuser chambercan be easily conece trolled to produce diffuser characteristics whichare matched with the impeller characteristics to obtain maximumefficiency.

It is, then, an object of this invention to provide a diffuser typecentrifugal pump which utilizes the kinetic energy of fiuid leaking pastseals in the pump for preventing the pump from becoming gas bound andfor lowering the intake pressure requirements of the pump.

A further object of the invention resides in the provision of a diffusertype centrifugal pump having mating bearing and inlet pieces which areeasily matched to balance the diffuser characteristics and impellercharacteristics for obtaining maximum efficiency.

A further object of the invention is to provide a compact light weightdiffuser type centrifugal pump adapted to deliver volatile fuels at highpressures without becoming gas bound and having concentric diffuser andcollecting passages for converting velocity heads into pressure heads.

A still further object of the invention is to provide the wear rings ofa shrouded impeller pump with a deflector ring that will direct uidleaking past the wear rings into the impeller for utilizing the kineticenergy of the Huid.

Another object of the invention is to provide a diffuser typecentrifugal pump with a smaller overall diameter than a conventionalstraight volute type centrifugal pump.

Another and specific object of the invention is to provide a ring ofaxially extending diffuser vanes around the periphery of a centrifugalimpeller to change the direction of flow of fluid'issuing from theimpeller while converting the velocity head of the fluid into a pressurehead and dis-- charging the iiuid radially inward at the and of itsaxial path.

Other and further objects of the invention will be apparent to thoseskilled in the art from the following detailed description of theannexed sheets of drawings which, by way of preferred examples,illustrate two embodiments of the invention:

On the drawings:

Figure l is an axial cross-sectional view, with parts in side elevation,of one form of pump according to this invention.

Figure 2 is a fragmentary exaggerated cross-sectional View of the wearring and deflector ring area of the pump of Figure 1.

Figure 3 is a transverse cross-sectional View, with parts in plan, takenalong the line III-III of Figure 1.

Figure 4 is a developed surface view around the circumference IV-IV ofFigure 3, but inverted to emphasize that the view is radially inwardtowardthe center of the assembly.

Figure 5 is an vaxial cross-sectional view, with parts in elevation, ofa second form of pump according to this invention.

- Figure 6 is a transverse cross-sectional view, with parts in plan,taken substantially along the line Vl-VI of Figure 5.

As shown on the drawings:

`In the first embodiment of the pump illustrated in Figures l to 4, thereference numeral 10 designates generally a diffuser type shroud-edimpeller centrifugal pump driven by a prime mover 1f1 such as anelectric motor, a turbine, or the like.

The pump 10 includes two main casing parts conveniently referred to as asuction inlet piece 12 and a bearing piece 1'3.

The bearing piece 13 has a generally cup-shaped diffuser .chamberdefining portion 114 with a circular opening 15 at one end thereof, anda reduced diameter hollow neck portion 16 extending from the center ofthe closed bottom end 17 thereof. The neck 16 extends to an outturnedflat circular flange 18 which, as shown, is connected around itsperiphery to the casing for the prime mover 11.

An anti-friction `balll bearing assembly 119 is mounted in the neck 16to rotatably support an impeller shaft 20 driven by the prime mover 11.A shaft seal assembly 21 is disposed around a reduced diameter portion20a of the shaft in t-he hollow neck 16. A shrouded centrifugal pumpimpeller 22 is secured on the end of the reduced diameter portion 20a ofthe shaft in the bottom of the cup shaped portion 14 of the bearingpiece. Suitable locking means 23 are provided to secure the impeller andshaft .in non-rotatable rel-ation.y A sleeve 24 bottomed on the bearingassembly 19 holds a shim 25 against a seal ring 26 which is seated in arecess in the flat bottom face of the impeller 22 to maintain the flatdisk portion 22a of the impeller in free running clearance relation withthe bottom wall 17 of the bea-ring piece 1-3. A seal ring 21a'of theassembly 21 rides on the ring 26. A well 27 in the neck .16 can bedrained through a port 28 closed by a plug 29 to prevent fluid leaking.past the seal 21 from entering the prime mover 11. This plug 29 ca-n bereplaced with a drain tube if desired.

The flat disk 22a of the impeller 22 has a frustoconical hub portion 22bextending toward the inlet piece 12. A plurality of upstanding curvedpumping vanes 22e are provided on the disk 22a in spaced concentricrelation around the hub 22b as best shown in Figure 3. These vanes 22edefine pumping channels 30 extending radially outward and peripherallylrearward from the -countenclockwise direct-ion of rotation of theimpeller. These pumping channels 30 discharge streams of uid in aradially outward and counterclockwise rotating direction into the bottomportion of the cup-shaped end 14 of the bearing piece 113 whereupon thediffuser vanes 31 .change the direction of ilow of the streams into anaxially extending spiral around the side wall of the cup 14.

As shown in the developed view of Figure 4, the difuser vanes 31 arespirally curved along their length to scoop up the counter-clockwisewhirling iluid from the impeller and deliver it to the open end of thecup 14 which has a lip or flange a surrounding the opening thereof. Thevaries 31 have rounded thickened end portions 31a merging into the range15a and, as shown in Figure 3, these portions form anchors for studs 32used to attach the inlet piece 12 to. t-he bearing piece 13.

.The side wall of the cup 14 has an outwardly extending hollow nippleportion 14a providing aI peripheral discharge outlet 33 for the pump. Asshown in Figure 4, this outlet 33 is positioned between the vanes 31 andis not bridged by a vane.

The inlet piece 12, as best shown in Figure l, has a cent-ralfrustconical port-ion 34 with Van outtur-ned flange 34a at the outer endthereof,V a disk-like portion 34h intermediate the ends thereof, and ashoulder 34e at the small inner end thereof. This shoulder'34c issurrounded by a cylindrical skirt 34d which extends to an outwardlyflaring end Wall 34e. The radial outer end of the aring portion 34e hasan axially extending rim 34f. A cylindrical Wall 34g surrounds the skirt34d in spaced concentric relation therefrom and extends beyond theshoulder 34e into spaced relation with the disklike portion 34b. TheWall 34g is on the outer end of the wall 34e. An annular trough 35 is:thereby provided on the small end of the tapered central portion 34 ofthe inlet piece 12 and this trough surrounds the inlet piece.

The disk portion 34b of the inlet piece 12A overliesl the cup 14 of thebearing piece and is apertured to receive the studs 32 therethrough.Nuts 36 on the studs attach the bearing and inlet pieces together. Aperipheral wall portion on the disk 34b snugly fits in the opening 15 ofthe cup 14 and is ,grooved to receive :a seal ring 37 for preventingleakage between the two pieces. When so mounted, the small end of theconical central portion 34 of the inlet piece extends into the centralpor-tion of the cup 14 and carries the wall 34g into snug tting relationwith the inner walls of the diffuser vanes 31. The diffuser vanes arethereby effective to discharge into the open end of the trough 35 andthe trough 35, in turn, has an opening 38 in its outer walrl 34g alignedwith the outlet 33 to discharge its contents through the outlet.

The impeller 22 has its shroud 22d overlying the pumping vanes 22C andhaving close-running clearance rel-ationship with the wall 34e and lip34f of the inlet piece. This shroud 22d also has anupstanding-cylindrical pon tion 22e extending into the skirt portion 34dof the inlet piece.

A wear ring 39 preferably composed of brass, is pressfitted around theupstanding cylindrical portion 22e of the shroud. This wear ring 39cooperates with a bearing ring 40 press fitted into the skirt 34d. Thetwo rings 39 and 40 .are in concentric close-'running clearancerelationship.

@In accordance with this invention, a deflector ring 41 is seated in theskirt 34d against the shoulder 34e and 'held thereagainst by the bearingring 40. This deector ring has a lip portion 41a projecting into thevupstanding cylindrical portion 22e of the impeller shroud, in spacedrelation inwardly from said shroud. The lip is tap-ered to provide atapered passageway, between the impeller and lip. It will be noted thatthe end of the' lip has a smaller diameter tha-n the impeller shroudopen- -ing and projects into this opening.

The central frusto-conical portion 34 of the inlet piece provides aconverging inlet 42 extending into the central Iportion or eye of thepump and discharging into the shroud of the impeller. At the point ofdischarge, however, the deector ring 41 projects into the converging endof the inlet passage 42. The luid fed to the eye or shroud of theimpeller is acted on by the pumping vanes and discharged into thediluser chamber 14a between the Acup 14 .and the outer wall 34g of thetrough. Thev channels 30 into the diffuser chamber 14a and ows in,

an axial spiral path to the end of this diffuser chamber where it againmakes a turn a-nd is discharged inwardly into the trough 35.y The uidenters the trough' in a substantially non-whirling condition since thediifl fuser vanes are designed to eliminate the rotational cornponent bythe time the fluid reaches the trough. The uid in the trough 35 thendischarges through the opening 35 into the outlet passage 33.

Since the impeller must have good running clearance' relationship withadjacent parts, and since high pressures are created by the pump, someleakage will occur asl illustrated in Figure 2, wherein high pressureliquid from the peripheral outer portion of the impeller can flowbetween the shroud 22d and Wall 34e and between the rings 39 and 40 asindicated by the arrows. However, the de# flector ring 41 is effectiveto turn the direction of ow of this leaking uid and cause it todischarge in the same direction as uid fed through the passageway 42onto the pump. The kinetic energy of the leaking uid thereby.

becomes effective to provide a jet pump action on the incoming fluid inthe passageway 42' and since this jet pump action surrounds the incominguid it will be effective to reduce the required inlet head pressures foreicient operation of the pump. uid before it enters the slower movingstream of incoming tiud in the inlet, the leakage path diverges orwidens toward the exit. n

If the pump is handling volatile fluids which tend to form a gas core inthe eye of the pump, the diuser ring will prevent the pump from becominggas bound, since it will discharge the high pressure uid around thiscore. and cause liquid to be continuously fed into the pump.. AV

drain port 43 closed by a plug 44 isl provided in the.- lower In orderto slow up the leakingpart of the side wall of the cup 14, so that thepump can be cleaned without separation of the pieces 12 and 13.

In the embodiment shown in Figures and 6, the pump 50 has a bearingpiece 51 carrying the trough and the inlet piece 52 carrying thediffuser vanes. As shown the inlet piece 52 has a cylindrical endportion 52a providing an inlet opening 53 and an enlarged cup shapedportion 521; providing the diffuser chamber 54. The spiral diffuservanes 55 are formed on this cup portion 52b. The open end of the cup 52hreceives the bearing portion 51 and this bearing portion carries amounting barrel 56 with anti-friction bearings 57 rotatably supporting adrive shaft 5S. A prime mover such as an air turbine 59 drives the shaft58. A shrouded impeller 60 is mounted on the end of the shaft andoverlies the end of the bearing portion in the juncture between theinlet 53 and diffuser chamber 54. The impeller 60 has pumping vanes 60amounted on a fiat disk 6011 and carrying a top shroud 60e with anupstanding cylindrical portion 60d extending into the inlet 53.

The cylindrical portion 52a of the inlet piece carries a bearing ring 61surrounding the shroud portion 60d and bottomed against a deflector ring62 having a lip 62a extending into the inlet 53 for defecting leakingfluid from between the bearing ring 61 and shroud 60d into the directionof fiow of fluid through the inlet S3 for the same purpose as describedhereinabove.

The bearing piece 51 provides the annular trough 63 which has its closedend adjacent the disk 60b of the impeller and its open end adjacent theopen end of the cup 52b.

As shown in Figure 6, the side wall of the cup 52b has an outlet nipple64 providing an outlet passage 65 and the trough 63 has an outletopening 66 aligned with this passage 65.

Fluid flowing through the inlet 53 is received by the pumping vanes 6fmof the impeller and is discharged into the diffuser chamber where it ispicked up by the diffuser vanes 55 and directed in an axial spiral pathalong the outer wall of the trough into the open end of the trough atthe other end of the diffuser chamber. The whirling liquid in the troughis then discharged through the opening 66 and passageway 65.

The impeller 6i) has a depending cylindrical skirt 60d on the disk 60bthereof and this skirt has close running clearance relation with abearing ring 67 carried by the bearing piece 51. This arrangementprovides a seal to slow up leakage beyond the impeller into the hollowcentral portion of the bearing piece. In addition, this hollow centralportion of the bearing piece has a seal assembly 68. Bleed holes (notshown) can be provided through the impeller to equalize pressure betweenthe hollow central portion of the bearing piece and the inlet side ofthe impeller. Therefore, the leakage past the wear ring 67 fiows back tothe suction side through the bleed holes and excessive pressure is notplaced on seal 68.

A hollow drain pin 69 between the seal 68 and the bearings 57 holds thebearing piece and inlet piece against rotation and provides a drainpassageway closed by a plug 70 in the bottom half of the pump.

The pump 50 operates in the same general manner as the pump if) and thedeector rings of the two pumps are eective to lower the inlet pressurehead requirements for efficient operation of the pump as well as toprevent the pump from becoming gas bound.

From the above description it should therefore be understood that thisinvention provides diffuser type cen trifugal pumps which are adapted tohandle highly volatile fluids without becoming gas bound and are capableof delivering very high pressures while withstanding very high speedoperation.

In describing the relationship between the collecting trough or annulusand the diffusion annulus containing the blades 31, in Figure 1 and thecomparable collecting trough or annulus 63 and diffusion chambercontaining blades 55 in Figure 5, applicant has referred to' thesetroughs as concentric or as having common centers or as nested. Thisnested relationship of the parts, men# tioned supra, provides maximumdiffusion and straightenv ing of the fluid prior to its ejection fromthe pump, with an absolute minimum of space requirement. For purposes ofdescription, the term concentric as applied to the present applicationhas a limited meaning and includes within its scope only parts which aresubstantially coextensive in an axial dimension and radially spaced fromone another thereby providing a true nested relation.

It will be understood that modifications and variations may be effectedwithout departing from the scope of the novel concepts of the presentinvention. i

I claim as my invention: i

l. A diffuser type centrifugal pump adapted to deliver highly volatilefuels at high pressures without becoming gas bound which comprises apump casing having a bearing piece and an inlet piece, a shroudedcentrifugal impeller rotatably carried by the bearing piece, one of saidpieces having an annular substantially enclosed trough therein which hasa radially extending peripheral opening at the side of the trough remotefrom the impeller, the other of said pieces having a diffuser chambersurrounding and concentric with the trough and equipped with axiallyextending helical diffuser vanes for receiving fluid from the impellerto direct the fiuid axially into the open end of the trough.

2. A diffuser type centrifugal pump which comprises a pump casing havinga central inlet, a peripheral outlet, and concentric outer diffuser andinner trough chambers connected to each other by an annular cut in theperiphery of the trough at one side thereof, a shrouded impeller in saidpump positioned to receive fluid from the central inlet and to dischargethe fluid into one end of the diffuser chamber for axial fiow throughthe diffuser chamber to the annular cut, into the trough and thence tothe peripheral outlet.

3. A diffuser type centrifugal pump which comprises a pump casing havinga central inlet, a peripheral outlet, and nested concentric diffuser andtrough chambers communicating with each other at one side by means of anannular cut in the outer periphery of the trough and the inner'periphery of the diffusing chamber and with the peripheral outlet, animpeller in said pump casing positioned to receive fiuid from the inletand centrifugally dicharge the fiuid into the side of the diffuserchamber remote from said cut, diffuser vanes extending substantially theentire axial width of the diffuser chamber and effective to change thedirection of oW of the fluid issuing from the impeller into a helicalpath along the axis of the impeller for converting the velocity head ofthe fluid into a pressurehead and for moving the fluid in a spiral patharound the outside of the trough and thence into the said cut of thetrough for flow back toward said impeller and to a peripheral dischargethrough the outlet.

4. A diffuser type centrifugal pump which comprises a pump casing havinga central inlet and a peripheral outlet, an impeller spanning thecentral inlet and arranged to centrifugally discharge fiuid transverselyof said inlet, means defining a diffuser chamber surrounding theimpeller and extending axially of the impeller, spiral vanes on theouter peripheral wall of said diffuser chamber arranged to change thedirection of flow of fiuid issuing from the impeller into flow in anaxially extending helical path through the diffuser chamber, and meansdefining an annular chamber having an axial open end receiving the fluidfrom the diffuser chamber for deflecting the uid inwardly and back uponitself axially to the entrance of a radially directed peripheral outletin the outer wa'll of said annular chamber for delivering the compressedfluid through both the inside and outside walls of said diffuserchamber.

5. In a diffuser type centrifugal pump, the improvef' ment of a pumpcasing having a central inlet, a periphcral outlet, and radially nestedconcentric annular diffuser and collector chambers connected to eachother by means of an annular slot at one side of said chambers wherebyflow of the fluid during diffusion is axial through said peripheraloutlet being connected to said collector chamber.

6. A diffuser type centrifugal pump comprising a pump casing having acentral inlet, a pump impeller spanning the inner end of the inlet andadapted to radially discharge fluid transversely of the inlet, said pumpcasing having an axially extending annular diffuser chamber surroundingthe impeller and extending axially away therefrom, helical diffuservanes in said chamber positioned to convert the centrifugallydischarging fluid from the impeller into an axially extending spiralpath while changing the velocity head of the fluid into a pressure head,and said casing having an annular collection chamber radially inward ofand concentric with said diffuser chamber and the vanes thereof incommunication with the diffuser chamber by means of an annular cut insaid diffuser chamber at the side thereof remote from the impellerwhereby fluid flows axially through the inlet, thence radially throughthe impeller, thence axially in one direction through the diffuserchamber, thence radially inwardly through said cut, and thence axiallyin the reverse direction into the collection chamber.

7. A diffuser type centrifugal pump which comprises a pump casing havinga bearing piece and an inlet piece, said bearing piece having acup-shaped end with a flat bottom and a cylindrical side wall providinga diffuser chamber, a hollow neck on the central portion of said flatbottom, a shaft projecting through said hollow neck and rotatablycarried thereby, a shrouded impeller mounted on said shaft in closerunning clearance relation with the bottom of the cup and having pumpingvanes between the shrouds thereof arranged to centrifugally dischargefluid from the inlet piece to the periphery of the cup at the flatbottom thereof, said inlet piece having a tapered inlet portion with atrough defining ring surrounding the small end thereof and an outturneddisk portion for spanning the open end of the cup for closing the openend of the cup, said trough portion overlying said impeller in closerunning clearance relation and having a peripheral wall spaced inwardlyfrom the side wall of the cup, diffuser vanes in the cup between theperipheral wall of the trough and the side wall of the cup and arrangedto direct fluid from the impeller in an axially extending spiral pathinto the open end of the trough, said peripheral wall of the trough andsaid side wall of the cup having aligned openings therethrough fordischarge of fluid, and a deilector ring in said central tapered inletpassageway arranged to deflect fluid leaking from the periphery of theimpeller back to the inlet passageway in the direction of flow of theincoming fluid for creating a jet pump action on the incoming fluid.

8. A diffuser type centrifugal pump which comprises a casing having abearing piece and an inlet piece, said bearing piece having asurrounding trough on the end thereof, a pump shaft rotatably carried bythe bearing piece, and an impeller on said shaft spanning the end ofthe` bearing piece and the closed end of the trough, said impellerhaving a shroud extending axially therefrom, said inlet piece having acylindrical inlet receiving said shroud and a cup-shaped portionsurrounding and concentric with the trough of the bearing piece, axiallyextending helical diffuser vanes on said cup-shaped portion andextending through the axial width thereof and positioned to deflectfluid from the periphery of the impeller in a helical path axially alongthe side walls of the cup and thence radially inwardly into the troughthrough an annular cut in the outer wall thereof, a peripheral outletfor saidtrough, and a deflector ring in said inlet extending into theshroud of the pump for deflecting fluid leaking from the periphery ofthe impeller back ft? the inlet to utilize the kinetic energy of theleaking fluid for inducing the flow of fluid into the impeller.

9. A diffuser type centrifugal pump comprising a pump casing havingaxially aligned impeller and collector ring chambers, a surroundingdiffuser chamber connecting said chambers and concentric with saidcollector chamber, a central inlet to the impeller chamber and aperipheral outlet for the collector ring chamber, an impeller in theimpeller chamber receiving fluid in the center thereof from the inletand centrifugally discharging the fluid from the periphery thereof intoone side of the diffuser chamber, and vanes in the diffuser chamberextending axially throughout substantially the entire axial width ofsaid diffuser chamber for directing the fluid to the other side thereofand into the collector ring chamber.

lO. in a diffuser-type centrifugal pump, the improvement of a pumpcasing having a central inlet, a peripheral outlet, an annular diffuserchamber having axially extending helical diffuser vanes extendingsubstantially the full axial width of'said chamber, a collector chamberconcentric with said diffuser chamber and an annular opening at one endof said chamber for directing flow from said diffuser chamber to saidcollector chamber, the inner wall of said diffuser chamber and the outerwall of the collector chamber comprising a single member.

ll. A diffuser-type centrifugal pump which comprises a pump casinghaving a central inlet and a peripheral outlet, an impeller spanning thecentral inlet and arranged to centrifugally discharge fluid radially ofsaid inlet, means defining a diffuser chamber surrounding the impellerand extending axially of the impeller, spiral axially extending vanes onthe outer peripheral wall of said diffuser chamber arranged to changethe flow of fluid issuing from the impeller into flow in an axiallyextending helical path through the diffuser chamber, and means definingan annular collector chamber Within and concentric with said diffuserchamber having an axial open end receiving the fluid from the diffuserchamber for deflecting the fluid radially inwardly and back upon itselfto discharge through a peripheral. outlet in said diffuser and collectorchambers,y each of said diffuser and collector chambers having an axialdimension substantially greater than its radial dimension and theopening between said chambers having an axial dimension substantiallyless than the axial dimension of said collector chamber.

12. A diffuser-type centrifugal pump which comprises a pump casinghaving a central inlet, a peripheral outlet, and concentric outerdiffuser and inner trough chambers connected to each other by an annularcut in the periphery of the trough at one side thereof, an impeller insaid pump positioned to receive fluid from the central inlet anddischarge the fluid into the side of the diffuser chamber opposite fromsaid cut for axial flow through the diffuser chamber to the annular cut,into the trough and thence to the peripheral outlet, each of saiddiffuser and trough chambers having an axial dimension substantiallygreater than its radial dimension and the annular cut between saidchambers having an axial dimension substantially equal Vto the radialdimension of said diffuser chamber.

13. A diffuser-type centrifugal pump which comprises a pump casinghaving a central inlet, a peripheral outlet, and concentric outerdiffuser and inner trough chambers connected to each other by an annularcut in the periphery of the trough at one side thereof, an impeller insaid pump positioned to receive fluid from the central inlet anddischarge the fluid into the side of the diffuser chamber opposite fromsaid cut for axial flow through the diffuser chamber to the annular cut,into the trough and thence to the peripheral outlet, each of saiddiffuser and trough chambers having an axial dimension substantiallygreater than its radial dimension and the annular cut between saidchambers having an axial dimension substantially less than the axialdimension of either of aaid diffuser or trough chambers.

14. A diffuser-type centrifugal pump which comprises a pump casinghaving a central inlet, a peripheral outlet, and concentric outerdiffuser and inner trough chambers connected to each other by an annularcut in the periphery of the trough at one side thereof, an irnpeller insaid pump positioned to receive iluid from the central inlet anddischarge the uid into the side of the diffuser charnber opposite fromsaid cut for axial flow through the diffuser chamber to the annular cut,into the trough and thence to the peripheral outlet, said diffuserchamber having an axial dimension several times as great as its radialdimension and overlying said trough chamber throughout a majority of itsaxial dimension, and said annular cut having an axial dimensionsubstantially less than the axial dimension of either of said chambers.

15. A diffuser-type centrifugal pump which comprises a pump casinghaving a central inlet, a peripheral outlet, and concentric outerdituser and inner trough chambers connected to each other by an annularcut in the periphery of the trough at one side thereof, an irnpeller insaid pump positioned to receive Huid from the central inlet anddischarge the fluid into the side of the diffuser chamber opposite fromsaid cut for axial flow through the diiuser chamber to the annular cut,into the trough 10 and thence to the peripheral outlet, said ditfuserchamber having an axial dimension several times as great as its radialdimension and overlying said trough chamber throughout a majority of itsaxial dimension, and said annular cut having an axial dimensionsubstantially equal to the radial dimension of said diffuser chamber.

References Cited in the le of this patent UNITED STATES PATENTS 717,096Harris Dec. 30, 1902 786,384 Richards Apr. 4, 1905 815,540 Krogh Mar.20, 1906 1,072,650 Price Sept. 9, 1913 1,525,884 Plummer Feb. 10, 19252,018,092 Rickert Oct. 22, 1935 2,207,317 Gear July 9, 1940 2,405,048Nickerson July 30, 1946 2,436,514 Jennings Feb. 24, 1948 2,444,100 HillJune 29, 1948 2,450,143 Howard Sept. 28, 1948 2,684,634 Schneider July27, 1954 FOREIGN PATENTS 786,795 France June 17, 1935

